Semiconductor light emitting device, illumination module, illumination apparatus, method for manufacturing semiconductor light emitting device, and method for manufacturing semiconductor light emitting element

ABSTRACT

A semiconductor light emitting device ( 10 ) is provided with a base substrate ( 12 ) and three LED chips ( 14 A,  14 B, and  14 C) disposed on the base substrate ( 12 ). Each LED chip ( 14 A,  14 B, and  14 C) includes a semiconductor multilayer structure ( 20 ) and has a rhombus shape with interior angles of approximately 60° and approximately 120° in plan view. Each semiconductor multilayer structure ( 20 ) has an HCP single crystal structure and includes a light emission layer ( 24 ). The LED chips ( 14 A,  14 B, and  14 C) are arranged on the base substrate ( 12 ) so as to face one another at a vertex forming the larger interior angle in plan view. With this arrangement, the LED chips ( 14 A,  14 B, and  14 C) as a whole form a substantially regular hexagonal shape.

RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 11/720,258filed on May 25, 2007, now U.S. Pat. No. 7,906,788 which is a §371application of PCT/JP2005/024007 filed on Dec. 21, 2005, which claimspriority from Japanese Application No. 2004-372319 filed on Dec. 22,2004 and Japanese Application No. 2005-307575 filed on Oct. 21, 2005. Aco-pending divisional application Ser. No. 12/695,076 was filed on Jan.27, 2010 and issued as U.S. Pat. No. 8,022,420.

TECHNICAL FIELD

The present invention relates to a semiconductor light emitting devicehaving a semiconductor light emitting element such as a light emittingdiode (hereinafter, “LED”) chip, and an illumination module and anillumination apparatus both using the semiconductor light emittingdevice. The present invention also relates to a manufacturing method forthe semiconductor light emitting device and for the semiconductor lightemitting element.

BACKGROUND ART

In comparison with incandescent and halogen lamps, LEDs have higherefficiency and longer lives. With the recent increase in the intensityof white LEDs, active studies have been made on application of the whiteLEDs to illumination purposes. Among various point light sources, LEDsare expected, owing to their property, to replace halogen lamps whichare currently in wide use for spot lighting at shops, museums, andshowrooms.

Unfortunately, however, a conventional white LED produces, on theirradiated surface, a beam spot distorted into a square shape. Forapplication to the illumination purpose, the beam spot distortion needsto be corrected. A white LED produces a square-shaped beam spot becausean LED chip (semiconductor light emitting element) constituting thewhite LED is rectangular and light is emitted mainly through asquare-shaped surface thereof (see, for example, JP 2001-15817-A).

Ideally, it is desirable to produce LED chips having a cylindricalshape. Yet, the chances are extremely small in view of productivity. Thereason lies in the dicing process, which is the final stage of LED chipmanufacturing, to cut a wafer into separate LED chips with a diamondwheel. It is practically impossible to cut the wafer intocylindrical-shaped LED chips having a diameter on the order of hundredsmicrons. A rectangular LED chip may be ground into a cylindrical shape,which is also virtually impractical in view of the chip size.

In view of the above, an LED chip having the shape of a substantiallyregular hexagonal prism is suggested for ensuring both high productivityand a close-to-circle beam spot. LED chips having the shape of asubstantially regular hexagonal prism can be manufactured withefficiency using the technique disclosed in JP 11-340507-A.

Here, with reference to FIG. 31, a description is given to themanufacturing method of LED chips having the shape of a substantiallyregular hexagonal prism, disclosed in JP 11-340507-A.

A single crystal substrate 300 has a hexagonal closest-packed lattice(hereinafter, simply “HCP”) crystal structure, such as GaN or SiC,having the (0001) plane on main surfaces. As shown in FIG. 31A, the HCPsingle crystal substrate 300 can be cleaved along the [1-210], [2-1-10],and [11-20] orientations. One of the crystallographic orientationscoincides with an orientation flat 302 of the single crystal substrate.For example, in the case where the [1-210] orientation is parallel tothe orientation flat 302, the [2-1-10] and [11-20] orientations extendat 60° and 120° to the orientation flat 302, respectively.

In view of the above, after forming such components as electrodes and asemiconductor multilayer structure containing a light emission layer(none of the components are illustrated) on the single crystal substrate300, cleavage guide grooves 304 are formed in the [1-210], [2-1-10], and[11-20] orientations indicated by doted lines in FIG. 31A. With theguide grooves 304, the single crystal substrate 300 is partitioned intohexagonal areas 306 each of which will be later formed into an LED chip.By cleaving along the guide grooves 304, the single crystal substrate isdivided into separate LED chips.

According to the above method, LED chips having the shape of a hexagonalprism are manufactured with efficiency. In addition, by cleaving alongthe crystallographic planes, chipping and cracking of the semiconductormultilayer structure at the time of dicing are suppressed.

Although the technique disclosed in JP 11-340507-A ensures improvedproductively, there is a problem that the single crystal substrate isnot fully used. More specifically, as shown in FIG. 31B, which is apartial enlarged view of FIG. 31A, portions of the semiconductormultilayer structure grown in substantially regular triangle areas 308,which are enclosed with the substantially regular hexagonal areas 306 tobe later formed into LED chips, are wasted without being used.

In view of the above problem, the present invention aims to provide asemiconductor light emitting device which, as a whole, has the shape ofa substantially regular hexagonal prism and yet allows the best possibleuse of the single crystal substrate with minimum wastage. The presentinvention also aims to provide an illumination module and anillumination apparatus both having the semiconductor light emittingdevice. The present invention also aims to provide a method formanufacturing the semiconductor light emitting device and a method formanufacturing a semiconductor light emitting element having the shape ofa substantially regular hexagonal prism.

DISCLOSURE OF THE INVENTION

To achieve the above aim, a first aspect of the present inventionprovides a semiconductor light emitting device including a basesubstrate and three light emitting elements. Each light emitting elementincludes a semiconductor multilayer structure with a light emissionlayer, and has a rhombus shape with interior angles of approximately 60°and approximately 120° in plan view. The three light emitting elementsare arranged on one main surface of the base substrate so as to togetherform a substantially regular hexagonal shape in plan view.

According to the structure stated above, the semiconductor lightemitting device is provided with three light emitting elements each ofwhich includes a semiconductor multilayer structure with a lightemission layer and has a rhombus shape with interior angles ofapproximately 60° and approximately 120°. The three light emittingelements are arranged on one main surface of a base substrate so as totogether form a substantially regular hexagonal shape in plan view.Consequently, the semiconductor light emitting device produces a beamspot closer to a circle than to a square. In addition, since eachsemiconductor multilayer structure has the rhombus shape, it is ensuredto make the maximum use of a single crystal substrate in manufacturingsuch semiconductor multilayer structures.

In a second aspect, the present invention provides a semiconductor lightemitting device including a base substrate and six light emittingelements. Each light emitting element includes a semiconductormultilayer structure with a light emission layer, and has asubstantially regular triangular shape in plan view. The six lightemitting elements are arranged on one main surface of the base substrateso as to together form a substantially regular hexagonal shape in planview.

According to the structure stated above, a semiconductor light emittingdevice is provided with six light emitting elements each of whichincludes a semiconductor multilayer structure with a light emissionlayer and has a substantially regular triangular shape in plan view. Thesix light emitting elements are arranged on one main surface of a basesubstrate so as to together form a substantially regular hexagonal shapein plan view. Consequently, the semiconductor light emitting deviceproduces a beam spot closer to a circle than to a square. In addition,since each semiconductor multilayer structure has a substantiallyregular triangular shape, it is ensured to make the best possible use ofa single crystal substrate in manufacturing such semiconductormultilayer structures.

In a third aspect, the present invention provides an illumination moduleincluding a mounting substrate and the semiconductor light emittingdevice that is provided in the first aspect of the present invention andmounted on the mounting substrate. In a fourth aspect, the presentinvention provides an illumination module including a mounting substrateand the semiconductor light emitting device that is provided in thesecond aspect of the present invention and mounted on the mountingsubstrate.

In a fifth aspect, the present invention provides an illuminationapparatus including, as a light source, the illumination module that isprovided in the third aspect of the present invention. In a sixthaspect, the present invention provides an illumination apparatusincluding, as a light source, the illumination module that is providedin the fourth aspect of the present invention.

In a seventh aspect, the present invention provides a manufacturingmethod for a semiconductor light emitting device. The method includes: agrowing step of growing a semiconductor multilayer structure thatincludes a light emission layer, on one main surface of a substrate ofwhich crystal structure is a hexagonal closest-packed single crystalstructure having a (0001) plane; a partitioning step of forming guidegrooves in [1-210], [2-1-10], and [11-20] orientations in at least oneof two main surfaces of the substrate so as to partition said at leastone main surface, except along a periphery thereof, into a plurality ofareas of a uniform shape; a cleaving step of cleaving the substrate intoa plurality of separate chips along the guide grooves; and a combiningstep of arranging two or more of the chips so as to together form asubstantially regular hexagonal shape in plan view.

According to the above method, guide grooves are formed in [1-210],[2-1-10], and [11-20] orientations in at least one of two main surfacesof a single crystal substrate of which crystal structure is a hexagonalclosest-packed single crystal structure having a (0001) plane. With theguide grooves, said at least one main surface, except along a peripherythereof, is cleaved into a plurality of areas of a uniform shape. Then,the substrate is cleaved into a plurality of separate chips along theguide grooves. To manufacture a semiconductor light emitting device, twoor more of the plurality of chips obtained by the cleaving are arrangedso as to together form a substantially regular hexagonal shape in planview. Consequently, the best possible use of the single crystalsubstrate is ensured. In addition, since the chips are arranged to forma substantially regular hexagonal shape in plan view, the resultingsemiconductor light emitting device produces a beam spot closer to acircle than to a square.

In an eighth aspect, the present invention provides a manufacturingmethod for a semiconductor light emitting device. The method includes: agrowing step of growing a semiconductor multilayer structure thatincludes a light emission layer, on one main surface of a substrate ofwhich crystal structure is a hexagonal closest-packed single crystalstructure having a (0001) plane; a partitioning step of forming guidegrooves in [1-210], [2-1-10], and [11-20] orientations in at least oneof two main surfaces of the substrate so as to partition said at leastone main surface, except along a periphery thereof, into a honeycombpattern with a plurality of substantially regular hexagonal areas; and acleaving step of cleaving the substrate into a plurality of separatechips along the guide grooves.

According to the above method, guide grooves are formed in [1-210],[2-1-10], and [11-20] orientations in at least one of two main surfacesof a single crystal substrate of which crystal structure is a hexagonalclosest-packed single crystal structure having a (0001) plane. With theguide grooves, said at least one main surface, except along a peripherythereof, is partitioned into a honeycomb pattern with a plurality ofsubstantially regular hexagonal areas. Then, the substrate is cleavedinto a plurality of separate chips along the guide grooves, wherebysemiconductor light emitting elements are obtained. By virtue of thepartitioning into a honeycomb pattern, the single crystal substrate iseconomically used with minimum wastage. In addition, since eachsemiconductor light emitting element has a substantially regularhexagonal shape by itself, the semiconductor light emitting elementproduces a beam spot closer to a circle than to a square.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 are views showing a semiconductor light emitting deviceconsistent with an embodiment 1 of the present invention;

FIG. 2 are views showing an LED chip constituting the semiconductorlight emitting device of the embodiment 1;

FIG. 3 is a view showing manufacturing steps of the semiconductor lightemitting device of the embodiment 1;

FIG. 4 is a view showing manufacturing steps of the semiconductor lightemitting device of the embodiment 1;

FIG. 5 are views showing a manufacturing step of the semiconductor lightemitting device of the embodiment 1;

FIG. 6 is a view showing manufacturing steps of the semiconductor lightemitting device of the embodiment 1;

FIG. 7 is a view showing manufacturing steps of the semiconductor lightemitting device of the embodiment 1;

FIG. 8 are views showing a semiconductor light emitting deviceconsistent with an embodiment 2 of the present invention;

FIG. 9 are views showing an LED chip constituting the semiconductorlight emitting device of the embodiment 2;

FIG. 10 is a view showing manufacturing steps of the semiconductor lightemitting device of the embodiment 2;

FIG. 11 are views showing a manufacturing step of the semiconductorlight emitting device of the embodiment 2;

FIG. 12 is a view showing manufacturing steps of the semiconductor lightemitting device of the embodiment 2;

FIG. 13 is a view showing manufacturing steps of the semiconductor lightemitting device of the embodiment 2;

FIG. 14 are views showing a semiconductor light emitting elementmanufactured by a method consistent with an embodiment 3 of the presentinvention;

FIG. 15 is a view showing steps of the manufacturing method of theembodiment 3;

FIG. 16 are views showing a step of the manufacturing method of theembodiment 3;

FIG. 17 is a view showing a step of the manufacturing method of theembodiment 3;

FIG. 18 is a view showing steps of the manufacturing method of theembodiment 3;

FIG. 19 is a view showing a manufacturing step of the manufacturingmethod of the embodiment 3;

FIG. 20 are views showing a semiconductor light emitting deviceconsistent with the embodiment 3;

FIG. 21 are views showing a semiconductor light emitting elementmanufactured by a method consistent with an embodiment 4 of the presentinvention;

FIG. 22 is a view showing steps of the manufacturing method of theembodiment 4;

FIG. 23 is a view showing a step of the manufacturing method of theembodiment 4;

FIG. 24 is a view showing steps of the manufacturing method of theembodiment 4;

FIG. 25 is a view showing a step of the manufacturing method of theembodiment 4;

FIG. 26 is an oblique view showing an LED module;

FIG. 27A is a plan view of the LED module, FIG. 27B is a sectional viewof the LED module taken along the line F-F of FIG. 27A, and FIG. 27C isan enlarged view showing a portion G of FIG. 27B;

FIG. 28A is a plan view showing the LED module without lenses, and FIG.28B is a view showing a pattern of pads disposed on a ceramic substrateconstituting the LED module;

FIG. 29A is an oblique view and FIG. 29B is a bottom view of anillumination apparatus;

FIG. 30 is an exploded perspective view of the illumination apparatus;and

FIG. 31 are views showing a conventional manufacturing method for asemiconductor light emitting device having a regular hexagonal shape.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a description is given to embodiments of the presentinvention, with reference to the accompanying drawings.

Embodiment 1

FIG. 1A is an oblique view and FIG. 1B is a plan view of a semiconductorlight emitting device 10 consistent with an embodiment 1 of the presentinvention. FIG. 1C is a sectional view of the semiconductor lightemitting device 10 substantially taken along the line A-A of FIG. 1B.Note that the components shown in the figures, including FIGS. 1A, 1B,and 1C, are not illustrated on the same scale.

The semiconductor light emitting device 10 includes: a base substrate 12having a substantially regular hexagonal shape; three LED chips 14A,14B, and 14C, shown as exemplary semiconductor light emitting elements,mounted on the base substrate 12; and a phosphor 16 covering all the LEDchips 14A-14C (upper and lateral surfaces thereof).

The three LED chips 14A-14C are all identical in structure. Thus, whenit is not necessary to distinguish one from another, the referencenumeral 14 is used without accompanying the letters A-C. FIG. 2A is anoblique view and FIG. 2B is a plan view of an LED chip 14.

As shown in FIG. 2B, the LED chip 14 is in a substantially rhombus shapewith interior angles □=60° and □=120°. The reason for choosing such arhombus shape will be described later.

The LED chip 14 includes a single crystal substrate 18 having the HCPcrystal structure and a semiconductor multilayer structure (multilayerepitaxial structure) 20. The semiconductor multilayer structure 20 iscomposed of a first conductive layer 22 of a first conductive type madeof p-GaN layer, a light emission layer 24 made of an InGaN/GaN multiplequantum well (hereinafter “MQW”) layer, a second conductive layer 26 ofa second conductive type made of an n-GaN layer in the stated order fromthe top (i.e. from the side further away from the single crystalsubstrate 18). The semiconductor multilayer structure 20 constitutes adiode. Note that the single crystal substrate 18 is made of an n-GaN andthe semiconductor multilayer structure 20 was epitaxially grown thereon.

When seen the LED chip 14 from the above, a corner portion of thesubstantially rhombus semiconductor multilayer structure 20 is removedin the shape of a substantially regular triangle. In the thicknessdirection of the layers, the removed portion extends from the firstconductive layer 22 to some midpoint in the second conductive layer 26.That is, as a result of the removal, an area of the second conductivelayer 26 is exposed in the shape of a regular triangle. On the trianglearea of the second conductive layer 26, an n-electrode is formed as asecond electrode 28. On the upper surface of the first conductive layer22, a p-electrode is formed as a first electrode 30. The secondelectrode 28 is made of a stack of Ti/Au films, whereas the firstelectrode 30 is made of a stack of Rh/Pt/Au films.

Referring back to FIG. 1, the base substrate 12 includes an insulatingsubstrate 32 made of AlN (aluminum nitride). On the upper surface of theinsulating substrate 32, a first conductive pattern 34, a secondconductive pattern 36, a third conductive pattern 38, and a fourthconductive pattern 40 are formed. Each of the first to fourth conductivepatterns 36-40 is made of a stack of Ti/Pt/Al films.

On the undersurface of the insulating substrate 32, a first power supplyterminal 42 is formed for anode and a second power supply terminal 44 isformed for cathode. Each of the power supply terminals 42 and 44 is madeof a stack of Ni/Au films. The first power supply terminal 42 iselectrically connected to the first conductive pattern 34 viaplated-through-holes 46 and 48, whereas the second power supply terminal44 is electrically connected to the fourth conductive pattern 40 viaplated-through-holes 50 and 54.

On the base substrate 12 having the above structure, the LED chips14A-14C are flip-chip mounted. The first electrode 30A of the LED chip14A is joined to part of the first conductive pattern 34 via metal bumps56. The first electrode 30B of the LED chip 14B is joined to part of thesecond conductive pattern 36 via metal bumps 58. The first electrode 30Cof the LED chip 14C is joined to part of the third conductive pattern 38via metal bumps 60. Similarly, the second electrode 28A of the LED chip14A is joined to part of the second conductive pattern 36 via a metalbump 62. The second electrode 28B of the LED chip 14B is joined to partof the third conductive pattern 38 via a metal bump 64. The secondelectrode 28C of the LED chip 14C is joined to part of the fourthconductive pattern 40 via a metal bump 66. As is clear from theabove-described connections, the LED chips 14A-14C are connected inseries as shown in FIG. 1D via the second and third conductive patterns36 and 38. Normally, the drive voltage of a diode made of a GaNsemiconductor is 3-4 V and thus the drive voltage of an LED array ofthree serially connected diodes is on the order of 12 V. Generally, a 12V power supply is used for driving electronic appliances. That is tosay, the semiconductor light emitting device 10 incorporated into anelectronic appliance is usable without requiring an additional powersource or a dedicated power circuit. It should be appreciated, however,that the LED chips 14A-14C may be connected in parallel or provided withtheir own terminals to be electrically independent.

The LED chips 14A-14C each of which is in a substantially rhombus shapeare arranged on the base substrate 12, so as to face one another at avertex forming the larger interior angle in plan view. That is, the LEDchips 14A-14C arranged on the base substrate 12 together form asubstantially regular hexagonal shape in plan view.

The phosphor 16 is shaped into a substantially regular hexagonal prismconforming to the overall shape formed by the LED chips 14A-14Caltogether. Strictly speaking, the phosphor 16 is substantially in theshape of a frustum of a regular hexagonal pyramid having tapered lateralsurfaces, for a later-described manufacturing reason. Yet, the taperangle is extremely small, so that the phosphor 16 is regarded to besubstantially in the shape of a regular hexagonal prism. As shown inFIG. 1B, the central axis of the hexagonal prism of the phosphor 16 ismade to substantially coincide with the central axis of the hexagonalshape formed by the LED chips 14A-14C altogether. The phosphor 16 ismade of powder of phosphor materials and impalpable particles of SiO₂dispersed in a transparent resin, such as silicone. The phosphormaterials include yellowish green phosphor powder such as(Ba,Sr)₂SiO₄:Eu²⁺ or Y₃(Al,Ga)₅O₁₂:Ce³⁺, and red phosphor powder such asSr₂Si₅N₈:Eu²⁺ or (Ca,Sr)S:Eu²⁺.

The semiconductor light emitting device 10 having the above structure ismounted on a printed wiring board or the like to be ready for use. Formounting, the first and second power supply terminal 42 and 44 aresoldered onto mounting pads of the printed wiring board. Here, by virtueof the substantially regular hexagonal shape of the base substrate 12, aplurality of semiconductor light emitting devices 10 may be arranged ina honeycomb pattern on the printed wiring board or the like at a highpackaging density.

On application of an electric current via the first and second powersupply terminals 42 and 44, each light emission layer 24 emits bluelight at a wavelength of 460 nm. Part of the blue light emitted from thelight emission layer 24 travels toward the first conductive layer 22 andis reflected toward the second conductive layer 26 by the firstelectrode 30, which is made of a material having high reflectivity. Partof the blue light emitted from the light emission layer 24 travelsdirectly toward the second conductive layer 26. After passing throughthe second conductive layer 26 and the single crystal substrate 18, theblue light is partly absorbed by the phosphor 16 to be converted intoyellowish green light and red light. A mixture of the blue light, theyellowish green light, and the red light produces white light, and thewhite light finally exits the phosphor 16 mainly from the upper surfacethereof. Similarly, blue light emitted from each light emission layer 24in a lateral direction (blue light emitted from the lateral surfaces ofeach semiconductor multilayer structure 20) is partly converted by thephosphor 16 into yellowish green light and red light. A mixture of theblue light, the yellowish green light, and the red light produces whitelight, and the white light exits the phosphor 16 mainly from the lateralsurfaces. Here, since the white light is emitted from the LED chips14A-14C arranged to form a substantially regular hexagonal shape in planview, the beam spot is more circular than that produced by aconventional square LED chip.

Next, a description is given to a manufacturing method of thesemiconductor light emitting device 10 consistent with the embodiment 1,with reference to FIGS. 3-7. In FIGS. 3-7, the materials of thecomponents of the semiconductor light emitting device 10 are denoted byreference numerals in the one thousands and its last two digitscorrespond to the reference numerals denoting the correspondingcomponents.

First, as shown in FIG. 3, a semiconductor multilayer structure 1020 isformed by epitaxially growing the following layers in the stated orderover the (0001) plane of an N-GaN single crystal substrate 1018 by MOCVD(Metal Organic Chemical Vapor Deposition) (Step A1). That is, an n-GaNlayer 1026 which will later constitute the second conductive layer 26(FIG. 1), an InGaN/GaN MQW light emission layer 1024 which will laterconstitute the light emission layer 24 (FIG. 1), a p-GaN layer 1022which will later constitute the first conductive layer 22 (FIG. 1) aresequentially deposited in the stated order. The single crystal substratemay alternatively be a sapphire substrate or a SiC substrate.

In order to create the area (the regular triangle area) for forming thesecond electrode 28 (FIG. 1), part of the n-GaN layer 1026, InGaN/GaNMQW light emission layer 1024, and p-GaN layer 1022 is removed by, forexample, dry etching (Step B1).

Next, a stack 1030 of Rh/Pt/Au films is formed on the upper surface ofthe p-GaN layer 1022 by, for example, electron beam evaporation (StepC1). The Rh/Pt/Au film stack 1030 will later constitute the firstelectrode 30 (FIG. 1).

On the regular triangle area, a stack 1028 of Ti/Au films which willlater constitute the second electrode 28 (FIG. 1) is formed (Step D1).

Referring now to FIG. 4, the surface of the single crystal substrate1018 facing away from the semiconductor multilayer structure 1020 isground by, for example, mechanical grinding, until the thickness reaches200 μm or so (Step E1).

Cleavage guide grooves 68 are formed in the ground surface of the singlecrystal substrate 1018 by, for example, dry etching (Step F1). The stepsF1 and G1 will be described later in more detail.

Along the guide grooves 68, the single crystal substrate 1018 is cleavedinto separate pieces, whereby LED chips 14 are obtained (Step G1).

In the above steps F1 and G1, the single crystal substrate is splitalong the crystallographic planes into LED chips each having a rhombusshape. Since this process of cleaving is disclosed in JP 11-340507-A, adescription is given only briefly with reference to FIG. 5.

As shown in FIG. 5A, the HCP single crystal substrate 1018, such as aGaN or SiC, having the (0001) plane on main surfaces can be cleaved inthe [1-210], [2-1-10], and [11-20] orientations. One of thecrystallographic orientations coincides with an orientation flat 70 ofthe single crystal substrate 1018. For example, in the case where the[1-210] orientation is parallel to the orientation flat 70, the [2-1-10]orientation extends at 60° to the orientation flat 70, and the [11-20]orientation extends at 120° to the orientation flat 70.

In view of the above, the guide grooves 68 (FIG. 4, Step F1) are formedin the [1-210], [2-1-10], and [11-20] orientations indicated by dotedlines in FIGS. 5A and 5B. With the guide grooves 68, the single crystalsubstrate 1018 is partitioned into rhombus areas. By cleaving along theguide grooves 68, the single crystal substrate 1018 is divided intoseparate LED chips. Cleavage along the crystallographic planes isadvantageous in that chipping and cracking of the semiconductormultilayer structure at the time of dicing are suppressed. Occurrencesof chipping and cracking adversely influence the rhombus shape ofsemiconductor multilayer structure. In addition, the leak current tendsto increase, which adversely affect the reliability. There is anotheradvantage that the single crystal substrate 1018 (semiconductormultilayer structure) is fully used without waste, except along theouter periphery where no more rhombus areas can be formed. That is, thebetter use of the single crystal substrate is ensured in comparison withthe conventional example shown in FIG. 31.

Now, with reference to FIGS. 6 and 7, a description is given to thesteps of manufacturing the base substrate 12 (FIG. 1) and of mountingthe LED chips 14 (FIG. 1) onto the base substrate 12. Note that FIGS. 6and 7 showing the manufacturing steps are sectional views taken alongthe line C-C passing through the semiconductor light emitting device 10shown in FIG. 1B.

First, as shown in FIG. 6, for forming plated-through-holes 46, 48, 50,54 (FIG. 1), through holes are formed through a ceramic sheet 1032 whichis made of AlN and not yet sintered. The through-holes are then filledwith a metal paste (tungsten (W) paste, for example). The entiresubstrate is then sintered to obtain a 300 μm thick insulation substrate1032 having plated through-holes 1046, 1048, 1050, and 1054. (Step H1)

Then, the undersurface of the insulating substrate 1032 is ground by,for example, mechanical grinding, until the thickness reaches 200 μm orso (Step J1).

In predetermined areas of the upper surface of the insulating substrate1032, stacks of Ti/Pt/Au films are formed by, for example, sputtering toprovide the first to fourth conductive patterns 34-40 (FIG. 1) (StepK1).

In predetermined areas of the undersurface of the insulating substrate1032, stacks of Ni/Au films are formed by, for example, plating toprovide the first and second power supply terminals 42 and 44 (FIG. 1)(Step L1).

At predetermined locations on the first to fourth conductive patterns34-40, metal bumps 1058, 1060, and 1066 are formed with gold (Au) (StepM1).

The LED chips 14A-14C are flip-chip mounted appropriately on the firstto fourth conductive patterns 34-40 (Step N1).

A silicone resin containing phosphor particles and thixotropy such asaerosil is applied by, for example, screen printing to cover all the LEDchips 14A-14C. Here, the silicon resin is shaped into a substantiallyregular hexagonal prism. The silicon resin is then thermally cured toform the phosphor 16. (Step Q1)

The insulating substrate 1032 is cut into separate pieces with a dicingblade DB (Step R1). Each piece constitutes a finished semiconductorlight emitting device 10. Note that a laser cutting may be employedinstead of the dicing blade.

According to the embodiment 1, the LED chips are manufactured usingcleavage along the crystallographic planes, to each have a rhombus shapein plan view. For implementing such cleavage, the semiconductormultilayer structures each including a light emission layer are grown onan HCP single crystal substrate. The HCP single crystal substrate isdivided into separate LED chips using the dicing blade DB, which is usedin the step R1 shown in FIG. 7, or a laser beam, so that the dicing maybe carried out along lines that may or may not coincide with thecrystallographic planes. In the case where the dicing is carried outalong the lines which do not coincide with the crystallographic planes,the semiconductor multilayer structures may be grown on a substrate,such as an Si substrate, not having the HCP crystal structure. Bydividing the substrate into pieces in a pattern shown in 5A, separateLED chips each having a rhombus shape can be obtained.

Note in the case of dicing with a dicing blade, there is a risk ofchipping and cracking of LED chips, and the risk increases when thewafer (i.e. the substrate) is hard. In the case of dicing with a laserbeam, it is preferable to carry out the dicing with a lowest possiblepower in order to avoid any damage to the light emission layers. In viewof the above, a thinner wafer is more preferable.

Embodiment 2

FIG. 8A is an oblique view of a semiconductor light emitting device 80.FIG. 8B is a plan view of a base substrate 82, which will be describedlater. FIG. 8C is a sectional view of the semiconductor light emittingdevice 80 taken along the line D-D of FIG. 8B.

The semiconductor light emitting device 80 is composed of the basesubstrate 82 having a substantially square shape, six LEDs 84A, 84B,84C, 84D, 84E, and 84F, as exemplary semiconductor light emittingelements, mounted on the base substrate 82, and a phosphor 86 coveringall the LEDs 84A-84F (upper and lateral surfaces).

The six LED chips 84A-84F are all identical in structure. Thus, when itis not necessary to distinguish one from another, the reference numeral84 is used without accompanying the letters A-F. FIGS. 9A and 9B areviews of an LED chip 84 seen obliquely from the above and the bottom,respectively.

As shown in FIGS. 9A and 9B, the LED chip 84 is in the shape of asubstantially regular triangular prism (i.e. a substantially regulartriangle in plan view). The reason for choosing such a triangular shapewill be described later.

The LED chip 84 has a semiconductor multilayer structure (multilayerepitaxial structure) 94 composed of a first conductive layer 88 of afirst conductive type made of a p-AlGaN layer, a light emission layer 90made of an AlGaN/InGaN MQW layer, a second conductive layer 92 of asecond conductive type made of an n-AlGaN layer deposited in the statedorder. The semiconductor multilayer structure 94 constitutes a diode. Aswill be later described, the semiconductor multilayer structure 94 wasepitaxially grown on a single crystal substrate 144 (FIG. 10) not on thebase substrate 82.

On the undersurface of the first conductive layer 88, a p-electrode isformed as a first electrode 96. Along one side of the upper surface ofthe second conductive layer 92, an n-electrode is formed as a secondelectrode 98. The first electrode 96 is made of a stack of Rh/Pt/Aufilms, whereas the second electrode 98 is made of a stack of Ti/Aufilms.

Referring back to FIG. 8, the base substrate 82 includes an insulatingsubstrate 100 made of AlN. On the upper surface of the insulatingsubstrate 100, a first conductive pattern 102, a second conductivepattern 104, a third conductive pattern 106, a fourth conductive pattern108, a fifth conductive pattern 110, and a sixth conductive pattern 112are formed. The first to sixth conductive patterns 102-112 are each madeof a stack of Ti/Pt/Al films.

On the undersurface of the insulating substrate 100, a first powersupply terminal 114 is formed for anode and a second power supplyterminal 116 is formed for cathode. Each of the power supply terminals114 and 116 is made of a stack of Ni/Au films. The first power supplyterminal 114 is electrically connected to the first conductive pattern102 via plated-through-holes 118 and 120, whereas the second powersupply terminal 116 is electrically connected to the second conductivepattern 104 via plated-through-holes 122 and 124.

The LED chips 84A-84F are mounted at predetermined locations of thefirst to sixth conductive patterns 102-112 formed on the base substrate82 having the above structure. Each LED 84 is so mounted that the firstelectrode 96 (FIG. 9B) faces downward and is appropriately joined topredetermined areas of the first to sixth conductive patterns 102-112via bonding layers (which will be described later) made of AuSn. Morespecifically, the LED 84A is joined to an area 102A shaped like atriangular peninsula via a bonding layer 126A. The LED 84B is joined tothe third conductive pattern 106 via a bonding layer 126B. The LED 84Cis joined to the fourth conductive pattern 108 via a bonding layer 126C.Similarly, the LED 84D is joined to an area 102B of the first conductivepattern 102 via a bonding layer (not illustrated). The LED 84E and theLED 84F are joined to the fifth and sixth conductive patterns 110 and112, respectively, via bonding layers (not illustrated). Needless tosay, the LEDs 84A-84F are joined in the state where the LEDs 84A-84F arepositioned to coincide with the triangles defined by the conductivepatterns.

Among the LEDs 84A-84F joined in the above manner, the LEDs 84A, 84B,and 84C are electrically connected in series. Similarly, the LEDs 84D,84E, and 84F are electrically connected in series. (Hereinafter, theserially connected LEDs 84A-84C are collectively referred to as a “firstLED array 128”, whereas the serially connected LEDs 84D-84F arecollectively referred to as a “second LED array 130”).

The first and second LED arrays 128 and 130 are identical in the mannerof how the respective LEDs are connected. Thus, with reference to FIG.8C, a description is given only to how the LEDs of the first LED array128 are connected.

The second electrode 98A of the LED 84A is electrically connected to thethird conductive pattern 106 via bridge wiring 132. Consequently, thesecond electrode 98A of the LED 84A and the first electrode 96B of theLED 84B are electrically connected. Note that the second electrode 98Aand the bridge wiring 132 are integrally formed as described later.

Similarly, the second electrode 98B of the LED 84B is electricallyconnected to the fourth conductive pattern 108 via bridge wiring 134.Consequently, the second electrode 98B of the LED 84B and the firstelectrode 96C of the LED 84C are electrically connected. Note that thesecond electrode 98B and the bridge wiring 134 are also integrallyformed as described later.

That is, the LEDs 84A, 84B, and 84C are connected in series via thebridge wiring 132 and 134 and the like.

In addition, the second electrode 98C of the LED 84C is electricallyconnected to the second conductive pattern 104 via bridge wiring 136.Note that the second electrode 98C and the bridge wiring 136 are alsointegrally formed as described later. In addition, the first electrode96A of the LED 84A is connected to the first conductive layer 102, asdescribed above.

Note that the bridge wiring 132, 134, and 136 are electrically insulatedfrom the semiconductor multilayer structures 94A, 94B, and 94C byinsulating films 138, 140, and 142 made of silicone nitride.

The same description applies to the connection of the second LED array130. That is, the first and second LED arrays 128 and 130 are connectedin parallel as shown in FIG. 8D.

By connecting three LEDs in series as above, the same advantage as thatachieved by the embodiment 1 is achieved regarding required powersource. It should be noted, however, that the LEDs 84A-84F may beconnected in a 2 series×3 parallel arrangement (i.e. the LEDs areserially connected in pairs and the serially connected LED pairs areconnected in parallel). Alternatively, the LEDs 84A-84F may be providedwith their own terminals to be electrically independent.

In addition, since the substantially regular triangle LEDs 84A-84F areso arranged on the base substrate 82 that one vertex of every LED 84 isdirected substantially to the same point in plan view. With thisarrangement, the LEDs 84A-84F on the base substrate 82 collectively forma substantially regular hexagon in plan view.

The phosphor 86 has a substantially cylindrical outer shape. Strictlyspeaking, the phosphor 86 is substantially in the shape of a frustum ofa cone having a tapered lateral surface, for a later-describedmanufacturing reason. Yet, the taper angle is extremely small, so thatthe phosphor 86 is regarded to be substantially in a cylindrical shape.The central axis of the cylindrical shape is made to substantiallycoincide with the central axis of the hexagonal shape formed altogetherby the LEDs 84A-84D. The phosphor 86 is made of a transparent resin,such as silicone, containing dispersed powder of phosphor materials ofat least one of each of four colors (blue, green, yellow, and red) aswell as impalpable particles of metal oxide, such as SiO₂. Examples ofblue phosphor materials include (Ba,Sr)MgAl₁₀O₁₇:Eu²⁺, and(Ba,Sr,Ca,Mg)₁₀(PO₄)₆Cl₂:Eu²⁺. Examples of green phosphor materialsinclude BaMgAl₁₀O₁₇:Eu²⁺, Mn²⁺, and (Ba,Sr)₂SiO₄:Eu²⁺. Examples ofyellow phosphor materials include (Sr,Ba)₂SiO₄:Eu²⁺. Examples of redphosphor materials include La₂O₂S:Eu³⁺, CaS:Eu²⁺, and Sr₂Si₅N₈:Eu²⁺.

Similarly to the semiconductor light emitting device 10 of theembodiment 1, the semiconductor light emitting device 80 having theabove structure is mounted on a printed wiring board or the like to beready for use.

On application of an electric current via the first and second powersupply terminals 114 and 116, each light emission layer 90 emitsultraviolet light at a wavelength of 380 nm. Part of the ultravioletlight is converted by the phosphor 86 into blue, green, yellow, and redlight. A mixture of the four colors of light produces white light. Here,since the white light is emitted from the LEDs 84A-84F arranged to forma substantially regular hexagonal shape in plan view, the beam spot ismore circular than a beam spot emitted by a conventional square-shapedLED chip. In addition, according to the embodiment 2, the phosphor 86 isin a cylindrical shape. Hence, the beam spot is even more circular thanthat consistent with the embodiment 1.

Next, a description is given to the steps of manufacturing thesemiconductor light emitting device 80 consistent with the embodiment 2,with reference to FIGS. 10-13. In FIGS. 10-13, the materials of thecomponents of the semiconductor light emitting device 80 are denoted byreference numerals in the two thousands and its last three digitscorrespond to the reference numerals denoting the respective components.

First, as shown in FIG. 10, a semiconductor multilayer structure 2094 isformed by epitaxially growing the following layers in the stated orderover the (0001) plane of the single crystal substrate 144 by, forexample, MOCVD (Step A2). That is, a GaN sacrificial layer (notillustrated), an n-AlGaN layer 2092 which will later constitute thesecond conductive layer 92 (FIG. 9), an AlGaN/InGaN MQW light emissionlayer 2090 which will later constitute the light emission layer 90 (FIG.9), a p-AlGaN layer 2088 which will later constitute the firstconductive layer 88 (FIG. 9) are sequentially deposited in the statedorder. Here, a sapphire substrate having the HCP crystal structure isused as the single crystal substrate 144.

In the surface of the semiconductor multilayer structure 2094, dividinggrooves 146 are formed to a depth reaching the single crystal substrate144, whereby the semiconductor multilayer structure 2094 is divided intoa number of regular triangle pieces (Step B2).

Passivation films 148 are formed with silicon nitride by, for example,sputtering (Step C2). The passivation films 148 coat the bottom surfacesand the side walls of the dividing grooves 146 (i.e. the lateralsurfaces of the regular triangle pieces of the semiconductor multilayerstructure 2094), as well as part of the upper surfaces of the regulartriangle pieces of the semiconductor multilayer structure 2094. Althoughthe passivation films 148 remain in the finished semiconductor lightemitting device 80, the passivation films 148 are not shown in thefigures, except in FIGS. 10 and 11.

Next, a stack of Rh/Pt/Au films is formed on the upper surface of thefirst conductive layer 88 by, for example, electron beam evaporation(Step D2), thereby to constitute the first electrode 96. In addition,cleavage guide grooves 150 are formed in the undersurface of the singlecrystal substrate 144 by, for example, dry etching (Step D2). Basically,the step of forming the guide grooves 150 is similar to the step F1(FIG. 4) of forming the guide grooves 68 (FIG. 4) consistent with theembodiment 1, except for the groove pattern. More specifically, in theembodiment 1, the guide grooves 68 are formed so as to partition thewafer into a plurality of rhombus areas (See FIG. 5). In the embodiment2, however, the guide grooves 150 are formed as shown in FIG. 11 so asto partition the wafer 152 into regular triangle areas.

By cleaving along the guide grooves 150, the single crystal substrate144 is divided into separate LED chips 154 (Step E2).

Similarly to the embodiment 1, by cleaving along the crystallographicplanes, chipping and cracking of the semiconductor multilayer structureat the time of dicing are suppressed. In addition, the semiconductormultilayer structure 2094 is fully used without waste, except along theouter periphery where no more regular triangle areas can be formed.Thus, similarly to the embodiment 1, the better use of the singlecrystal substrate is ensured in comparison with the conventional exampleshown in FIG. 31.

Now, with reference to FIGS. 12 and 13, a description is given to thesteps of manufacturing the base substrate 82 (FIG. 8) and of mountingthe LED chips 84 onto the base substrate 82. Note that FIGS. 12 and 13showing the manufacturing steps are sectional views taken along the lineE-E of the semiconductor light emitting device 80 shown in FIG. 8B.

First, an insulating substrate 2100 made of AlN and havingplated-through-holes 118-124 (not illustrated in FIG. 12, see FIG. 8) isprepared (Step F2).

In predetermined areas of the upper surface of the insulating substrate2100, stacks of Ti/Pt/Au films are formed by, for example, sputtering,thereby to provide the first to sixth conductive patterns 102-112 (FIG.8). In addition, in predetermined areas of the upper surface of theinsulating substrate 2100, stacks of Ni/Au films are formed by, forexample, plating, thereby to provide the first and second power supplyterminals 114 and 116 (FIG. 8). (Step G2)

In predetermined areas of the first to sixth conductive patterns 102-112(FIG. 8), an AuSn films 2126A-2126F (2126D-2126E are not shown in thefigure) are formed by, for example, plating (Step H2). The AuSn films2126A-2126F will later constitute the bonding layers 126.

Each LED chip 154 obtained in the step E2 is joined to the insulatingsubstrate 2100 (Step J2). More specifically, the first electrode 96 isfaced downward, and the AuSn film 2126 is pressed against the firstelectrode 96. In this state, the AuSn film 2126 is heated to be fusedand joined to the first electrode 96.

Next, to remove the single crystal substrates (sapphire substrates) 144from the LED chips, the single crystal substrates 144 are irradiatedwith a YAG laser beam LB of a third harmonic emitted at 355 nm. Thelaser beam LB passes through the single crystal substrates (sapphiresubstrates) 144 without being absorbed. Absorption of the laser beam LBoccurs exclusively at the GaN sacrificial layers (not illustrated), sothat exothermic heat is locally developed. The local heat inducesdecomposition of the GaN bond in the vicinity of the interfaces of theGaN sacrificial layers. As a result, the single crystal substrates(sapphire substrates) 144 come to be separated from the semiconductormultilayer structures 94 (second conductive layers 92) in terms of thecrystal structure. Yet, the single crystal substrates 144 are stillphysically attached to the semiconductor multilayer structures 94 vialayers containing metallic Ga. The single crystal substrates 144 arecompletely removed from the semiconductor multilayer structures 94 byimmersion in, for example, a hydrochloric acid to dissolve portions inthe vicinity of the interfaces. (Step K2)

Next, to form the insulating films 138, 140, and 142, silicon nitridefilms are formed to coat lateral surfaces of the semiconductormultilayer structure 94 by, for example, sputtering (Step L2).

Next, stacks of Ti/Pt/Au films are formed by, for example, sputtering inpredetermined areas to provide the second electrodes 98A-98C as well asbridge wiring 132, 134, and 136 (Step M2).

A silicone resin containing phosphor particles and thixotropy such asaerosil is applied by, for example, screen printing to cover all theLEDs 84A-84F (LEDs 84D and 84F are not illustrated in FIG. 13). Here,the silicon resin is applied substantially into a cylindrical shape andthermally cured to form the phosphor 86. (Step N2)

The insulating substrate 2100 is cut into pieces with a dicing blade DB(Step Q2). Each piece constitutes a finished semiconductor lightemitting device 80.

According to the embodiment 2, the LED chips are manufactured usingcleavage along the crystallographic planes, to each have a substantiallyregular triangular shape in plan view. For implementing such cleavage,the semiconductor multilayer structures each including a light emissionlayer are grown on an HCP single crystal substrate. The HCP singlecrystal substrate is divided into separate LED chips using the dicingblade DB, which is used in the step Q2 shown in FIG. 13, a laser beam,or wet etching, so that the dicing may be carried out along lines thatmay or may not coincide with the crystallographic planes. In the casewhere the dicing is carried out along the lines which do not coincidewith the crystallographic planes, the semiconductor multilayerstructures may be grown on a substrate, such as an Si substrate, nothaving the HCP crystal structure. By dividing the substrate into piecesin a pattern shown in 11A, separate LED chips each having asubstantially regular triangular shape can be obtained.

Note in the case of dicing with a dicing blade, there is a risk ofchipping and cracking of LED chips, and the risk increases when thewafer (i.e. the substrate) is hard. In the case of dicing with a laserbeam, it is preferable to carry out the dicing with a lowest possiblepower in order to avoid any damage to the light emission layers. In viewof the above, a thinner wafer is more preferable.

Embodiment 3

FIG. 14 show an LED chip 400 which is a semiconductor light emittingelement manufactured by the method consistent with an embodiment 3 ofthe present invention. FIG. 14A is a plan view of the LED chip 400 andFIG. 14B is a sectional view taken along the line G-G of FIG. 14A.

As shown in FIG. 14A, the LED chip 400 is in a substantially regularhexagonal shape in plan view. As shown in FIG. 14B, the LED chip 400 iscomposed of a single crystal substrate 402 and a semiconductormultilayer structure (multilayer paraxial structure) 404. Thesemiconductor multilayer structure 404 is composed of a first conductivelayer 406 of a first conductive type made of a p-GaN layer, a lightemission layer 408 made of an InGaN/GaN MQW layer, a second conductivelayer 410 of a second conductive type made of an n-GaN layer in thestated order from the top (i.e. from the side further away from thesingle crystal substrate 402). The semiconductor multilayer structure404 constitutes a diode. Note that the single crystal substrate 402 ismade of an n-GaN, and the semiconductor multilayer structure 404 wasepitaxially grown thereon.

When seen the LED chip 400 from the above, a corner portion of thesubstantially regular hexagonal semiconductor multilayer structure 404is removed in a substantially rhombus shape. In the thickness directionof the layers, the removed portion extends from the first conductivelayer 406 to some midpoint in the second conductive layer 410. That is,as a result of the removal, an area of the second conductive layer 410is exposed in the shape of a rhombus. On the rhombus area of the secondconductive layer 410, an n-electrode is formed as a second electrode412. On the upper surface of the first conductive layer 406, ap-electrode is formed as a first electrode 414. The second electrode 412is made of a stack of Ti/Au films, whereas the first electrode 414 ismade of a stack of Rh/Pt/Au films.

As shown in FIG. 14A, each vertex of the substantially regular hexagonalLED chip 400 (portions denoted by the reference numeral 413) is cut awayto leave an arc-shaped recess. Each arc-shaped recess is cut to curveinward towards the center of the single crystal substrate. Theserecesses are present as a result of holes 162 (FIG. 17) formed in orthrough a wafer 156 in a later-described manufacturing step. Inaddition, portions 415 of the lateral sides of LED chip 400 are slanted,as shown in FIG. 14B, as a result of guide grooves 164 (FIG. 18) formedin the surface of the wafer 156 in a later-described manufacturing step.

Now, a description is given to a manufacturing method of the LED chip400 having the above structure, with reference to FIGS. 15-19. In FIGS.15-19, the materials of the components of the LED chip 400 are denotedby reference numerals in the three thousands and its last three digitscorrespond to the reference numerals denoting the correspondingcomponents.

First, as shown in FIG. 15, a semiconductor multilayer structure 3404 isformed by epitaxially growing the following layers in the stated orderover the (0001) plane of an n-GaN single crystal substrate 3402 byMOCVD. That is, an n-GaN layer 3410 which will later constitute thesecond conductive layer 410 (FIG. 14), an InGaN/GaN MQW light emissionlayer 3408 which will later constitute the light emission layer 408(FIG. 14), a p-GaN layer 3406 which will later constitute the firstconductive layer 406 (FIG. 14) are deposited in the stated order. Then,a stack 3414 of Rh/Pt/Au films is formed on the upper surface of thep-GaN layer 3406 by, for example, electron beam evaporation. TheRh/Pt/Au film stack 3414 will later constitute the first electrode 414(FIG. 14). (Step A3)

In order to create the area (the rhombus area) for forming the secondelectrode 412 (FIG. 14), part of the n-GaN layer 3410, InGaN/GaN MQWlight emission layer 3408, p-GaN layer 3406, and Rh/Pt/Au film stack3414 is removed by, for example, dry etching (Step B3).

On the rhombus area, a stack 3412 of Ti/Au films which will laterconstitute the second electrode 412 (FIG. 14) is formed (Step C3).

FIG. 16A is an enlarged plan view of the wafer 156 in the state wherethe Step C3 is done. As shown in FIG. 16A, on the wafer 156, a pluralityof substantially regular hexagons 158 (hereinafter, simply “regularhexagon 158”) are formed each with a Ti/Au film stack 3412 and anRh/Pt/Au film stack 3414 that is laid on the semiconductor multilayerstructure 3404 (FIG. 15, Step C3). For the purpose of clearillustration, FIG. 16B shows the entire wafer 156 with broken linesrepresenting midlines 160 passing through midpoints between boundariesof adjacent regular hexagons 158. As shown in FIG. 16B, the wafer 156 ispartitioned into a honeycomb pattern with a hexagonal arrangement. Thatis, the wafer 158 is partitioned into areas of a uniform shape (regularhexagon), except along the periphery of the wafer 156. In addition, eachside of each hexagon 158 coincides with one of the [1-210], [2-1-10],[11-20] orientations. The reason for choosing such partitioning will bedescribed later.

Referring back to FIG. 15, the surface of the single crystal substrate3402 facing away from the semiconductor multilayer structure 3404 isground by, for example, mechanical grinding, until the thickness reaches100 μm or so (Step D3).

Next, as shown in FIG. 17, a hole 162 is formed at each location pointedby a vertex of each of three adjacent regular hexagons 158 (Step E3). Inother words, as in the enlarged portion K shown in FIG. 17, a hole 162is formed at each location where vertexes of three adjacent regularhexagons defined by the midlines 162 meet. The holes 162 may be formedby, for example, dry etching or laser. In addition, the holes 162 may bethrough holes or non-through holes. Yet, in the case of non-throughholes, the depth need to be greater than the depth of guide grooves 164which will be described later. The reason for forming the holes 162 willalso be described later.

Next, as shown in FIG. 18, the cleavage guide grooves 164 are formed by,for example, dry etching in the surface of the wafer 156 from the sideof the semiconductor multilayer structure 3404 (Step F3). The guidegrooves 164 are formed along the midlines 160 (FIGS. 16 and 17), so thatthe single crystal substrate 3402 is partitioned into a honeycombpattern with hexagonal areas. It goes without saying that each side ofeach hexagonal area coincides with one of the [1-210], [2-1-10], [11-20]orientations.

Next, an elastic sheet 168 is adhesively attached to the single crystalsubstrate 3402, and the wafer 156 is mounted over a table 170 viaanother elastic sheet 166. A substantially spherical pressure-applyingmember 172 made of an elastic material is rolled over the sheet 168 inthe arrowed direction shown in FIG. 19 across the wafer 156 a severaltimes. While rolling, the pressure-applying member 172 is pressedagainst the sheet 168 (i.e. pressure is applied to the single crystalsubstrate via the sheet 168). (Step G3)

As a result, the wafer 156 (single crystal substrate 3402) is cleavedalong the guide grooves 164 into separate LED chips (Step H3).

In the case where guide grooves extend linearly across the wafer as inthe embodiments 1 and 2 (FIGS. 5 and 11), cleaving is carried outwithout a problem. However, as in the embodiment 3 where guide groovesis formed in a complex pattern, cleaving involves a risk of cracks atunexpected locations (locations other than the guide grooves). That is,a crack produced along one line segment of the guide grooves developsbeyond the end point of the line segment. In order to prevent suchunintentional cracks, the embodiment 3 provides the holes 162 (FIG. 17)described above. The presence of the holes 162 stops the cracks fromrunning any farther, so that there will be no unintentional cracks.

Similarly to the embodiments 1 and 2, by cleaving along thecrystallographic planes, chipping and cracking of the semiconductormultilayer structure at the time of dicing are suppressed. Alsosimilarly to the embodiments 1 and 2, in addition, the single crystalsubstrate 3402 is fully used without waste, except for the peripherywhere no more regular hexagonal areas can be formed. That is, the betteruse of the single crystal substrate 3402 is ensured in comparison withthe conventional example shown in FIG. 31. More specifically, in theembodiment 3 similarly to the embodiments 1 and 2, the single crystalsubstrate is partitioned into areas of a uniform shape with the guidegrooves, and divided into separate pieces (LED chips) along the guidegrooves. Consequently, the single crystal structure substrate is usedwith minimum wastage.

In addition, according to the embodiment 3, each LED chip 400 in itselfis has a substantially regular hexagonal shape. Thus, unlike theembodiments 1 and 2, it is not necessary to use a plurality of LED chipsin combination. Note that it goes without saying that the LED chip 400may be used in combination with a phosphor (by disposing the phosphor tocover the LED chip 400) to constitute a white LED.

It is also applicable, of course, that a plurality of LED chips 400 maybe used in combination to constitute a semiconductor light emittingdevice, similarly to the embodiments 1 and 2.

FIG. 20 show an example of such a semiconductor light emitting device.

FIG. 20A shows a semiconductor light emitting device 420 composed ofseven LED chips 400 arranged to form, as a whole, a substantiallyregular hexagonal shape in plan view.

The semiconductor light emitting device 420 is basically similar instructure to the semiconductor light emitting device 10 (FIG. 1) of theembodiment 1, except the conductive patterns and the like formed on theinsulating substrate. Thus, no detailed description is given.

FIG. 20B shows a semiconductor light emitting device 422 composed ofnineteen LED chips 400 arranged to form, as a whole, a substantiallyregular hexagonal shape in plan view.

The semiconductor light emitting device 422 is basically similar instructure to the semiconductor light emitting device 10 (FIG. 1) of theembodiment 1, except the conductive patterns and the like formed on theinsulating substrate. Thus, no detailed description is given.

Embodiment 4

The LED chip 400 consistent with the embodiment 3 above is designed forflip-chip mounting and has both the p- and n-electrodes on the same mainsurface of the single crystal substrate. On the contrary, an LED chip500 manufactured in the method consistent with an embodiment 4 of thepresent invention has a p-electrode and an n-electrode on mutuallydifferent main surfaces of the single crystal substrate.

FIG. 21A is an oblique view and FIG. 21B is a plan view of the LED chip500. FIG. 21B is a sectional view of the LED chip 500 taken along theline H-H of FIG. 21B.

As shown in FIG. 21B, the LED chip 500 is in a substantially regularhexagonal shape in plan view. As shown in FIGS. 14A and 14B, the LEDchip 500 is composed of an HCP single crystal substrate 502 and asemiconductor multiplayer structure (multilayer epitaxial structure)504. The semiconductor multilayer structure 504 is composed of a firstconductive layer 506 of a first conductive type made of p-GaN layer, alight emission layer 508 made of an InGaN/GaN MQW layer, a secondconductive layer 510 of a second conductive type made of an n-GaN layerin the stated order from the top (from the side further away from theHCP single crystal substrate 502). The semiconductor multilayerstructure 504 constitutes a diode. Note that the HCP single crystalsubstrate 502 is made of an n-GaN substrate on which the semiconductormultilayer structure 504 was epitaxially grown.

On the entire surface of the first conducive layer 506, a transparentelectrode 512 made of ITO coating is formed. On the upper surface of thetransparent electrode 512, a contact electrode 514 made of a stack ofTi/Pt/Au films is formed. In this embodiment, the transparent electrode512 and the contact electrode 514 constitute a first electrode 514,which is a p-electrode. The contact electrode 514 is composed of aregular hexagonal rim portion and a spoke portion extending from thecenter of the hexagon to the vertexes of the hexagonal rim.

On the entire undersurface of the single crystal substrate 502, ann-electrode is formed as a second electrode 518. The second electrode ismade of a stack of Ni/Ag/Pt/Au films.

As shown in FIGS. 21A and 21B, each vertex of the substantially regularhexagonal LED chip 500 (portions denoted by the reference numeral 517)is cut away to leave an arc-shaped recess. Each arc-shaped recess is cutto curve inward towards the center of the single crystal substrate.These recesses are present as a result of holes 178 (FIG. 25) formed inor through a wafer 174 in a later-described manufacturing step. Inaddition, portions 519 of the lateral sides of LED chip 500 are slanted,as shown in FIG. 21 C, as a result of guide grooves 182 (FIG. 24) formedin the surface of the wafer 174 in a later-described manufacturing step.

When mounting the LED chip 500 having the above structure onto, forexample, a printed wiring board, the second electrode 518 is bondeddirectly to a bonding pad of the printed wiring board. In addition, thefirst electrode 516 is electrically connected at the center thereof(where the spokes meet) to another bonding pad of the printed wiringboard with a bonding wire.

Next, a description is given to the manufacturing method of the LED chip500, with reference to FIGS. 22-25. In FIGS. 22-25, the materials of thecomponents of the LED chip 500 are denoted by reference numerals in thefour thousands and its last three digits correspond to the referencenumerals denoting the corresponding components.

First, as shown in FIG. 22, a semiconductor multilayer structure 4504 isformed by epitaxially growing the following layers in the stated orderover the (0001) plane of an n-GaN single crystal substrate 4502 by MOCVD(Step A4). That is, an n-GaN layer 4510 which will later constitute thesecond conductive layer 510 (FIG. 21), an InGaN/GaN MQW light emissionlayer 4508 which will later constitute the light emission layer 4508(FIG. 21), a p-GaN layer 4506 which will later constitute the firstconductive layer 506 (FIG. 21) are sequentially deposited in the statedorder.

Portions the semiconductor multiplayer structure 4504 (i.e. portions ofthe n-GaN layer 4510, InGaN/GaN MQW layer 4508, p-GaN layer 4506) areremoved to a depth reaching some midpoint in the n-GaN layer 4510 by,for example, dry etching, so as to leave a plurality of regularhexagonal prisms formed with the upper part of the semiconductormultilayer structure 4504 (Step B4). FIG. 23 is an enlarged view of aportion the wafer 174 in the state where the step B4 is done. As shownin FIG. 23, the semiconductor multiplayer structure 4504 is partitionedinto substantially regular hexagonal shapes 176 in plan view(hereinafter, simply “regular hexagons 176”). The pattern in which theregular hexagons 176 are arranged are identical to that described in theembodiment 3 (see for example FIG. 16).

Referring back to FIG. 22, an ITO coating 4512 is formed on the uppersurface of the p-GaN layer 4508 by, for example, sputtering (Step C4).The ITO coating 4512 will later constitute the transparent electrode 512(FIG. 21).

Next, a stack of Ti/Pt/Au films 4516 is formed by, for example, electronbeam evaporation (Step D4). The Ti/Pt/Au film stack 4516 will laterconstitute the contact electrode 516 (FIG. 21).

The surface of the single crystal substrate 4502 facing away from thesemiconductor multilayer structure 4504 is ground by, for example,mechanical grinding, until the thickness reaches 100 μm or so (Step E4).

Referring now to FIG. 24, a stack of Ni/Ag/Pt/Au films 4518 is formed onthe ground surface of the single crystal substrate 4504 (Step F4). TheNi/Ag/Pt/Au film stack will later constitute the second electrode 518(FIG. 21).

Next, as shown in FIG. 25, holes 178 are formed for the similar reasonto the embodiment 3, i.e. for preventing occurrences of undesirablecracks at the time of cleavage, (Step G4). Note that the broken linesshown in FIG. 25 represent midlines 180 between boundaries of adjacentregular hexagons 176.

Referring back to FIG. 24, cleavage guide grooves 182 are formed by, forexample, dry etching in the surface of the wafer 174 from the side ofthe semiconductor multilayer structure 4504 (Step H4). The guide grooves182 are formed along the midlines 180 (FIG. 25), so that the singlecrystal substrate 4502 is partitioned into a honeycomb pattern withhexagonal areas. It goes without saying that each side of each hexagonalarea coincides with one of the [1-210], [2-1-10], [11-20] orientations.

Next, similarly to the embodiment 3, an elastic sheet 168 is adhesivelyattached to the wafer 174, and the wafer 174 is mounted over a table 170via another elastic sheet 166. A substantially sphericalpressure-applying member 172 made of an elastic material is rolled overthe sheet 168 across the wafer 174 a several times while pressing thepressure-applying member 172 against the sheet 168. (Step J4)

As a result, the wafer 174 (single crystal substrate 4502) is cleavedalong the guide grooves 182 and divided into separate LED chips 500(Step K4).

The LED chips 500 are removed from the sheets 166 and 168 to be readyfor use.

The manufacturing method of the embodiment 4 achieves the same effect asthat achieved by the embodiment 3. Thus, no disruption is given thereto.

Also similarly to the embodiment 3, a plurality of LED chips 500 may beused to constitute a semiconductor light emitting device by arrangingthe LED chips 500 to together form a substantially regular hexagonalshape.

Embodiment 5

FIG. 26 is an external oblique view of a white LED module 200 having thesemiconductor light emitting devices 10 consistent with the embodiment 1(hereinafter simply “LED module 200”). Instead of the semiconductorlight emitting devices 10, the LED module 200 may have the semiconductorlight emitting devices 80 (see FIG. 8, for example) consistent with theembodiment 2, or the semiconductor light emitting devices 420 or 422(See FIG. 20) consistent with the embodiment 3. Yet, in this embodiment,a description is given as an example to the LED module 200 having thesemiconductor light emitting devices 10 consistent with theembodiment 1. Note that the LED module 200 is fixed to a later-describedillumination fixture 240 (FIG. 29) to be ready for use.

The LED module 200 includes, as a mounting substrate, a circular ceramicsubstrate 202 which measures 5 cm in diameter and made of AlN. The LEDmodule 200 also includes three glass lenses 204, 206, and 208. Theceramic substrate 202 is provided with a guide notch 210 for attachmentto the illumination fixer 240, and positive and negative terminals 212and 214 for power supply from the illumination fixture 240.

FIG. 27A is a plan view of the LED module 200. FIG. 27B is a sectionalview of the LED module 200 taken along the line F-F of FIG. 27A. FIG.27C is an enlarged view showing a portion G of FIG. 27B.

As shown in FIGS. 27A and 27B, the ceramic substrate 202 has a guidehole (through hole) 216 at the center thereof, for attachment to theillumination fixture 240. In addition, the undersurface of the ceramicsubstrate 202 is coated with gold plating 217 in order to improvethermal dissipation.

The semiconductor light emitting devices 10 (numbering three in total)are mounted on the ceramic substrate 202 each at a locationcorresponding to the center of a respective one of the lenses 204, 206,and 208 illustrated as a circle in FIG. 27A.

The ceramic substrate 202 is a stack of two ceramic substrates 201 and203 each of which is 0.5 mm thick and made mainly of AlN. Alternativelyto AlN, the ceramic substrates 201 and 203 may be made of variousmaterials including Al₂O₃, BN, MgO, ZnO, SiC, and diamond.

The semiconductor light emitting devices 10 are mounted on the ceramicsubstrate 201, which is the lower layer, in a manner that the first andsecond power supply terminals 42 and 44 (see FIG. 1) face toward theceramic substrate 201. The ceramic substrate 203, which is the upperlayer, is provided with downwardly and internally tapered through holes215 each for securing mounting space of a semiconductor light emittingdevice 10. In other words, the ceramic substrate 202 has recesses eachof which is diametrically larger toward the opening, and eachsemiconductor light emitting device 10 is mounted on the bottom of arespective one of the recesses. Yet, the through holes forming therecesses do not have to be tapered. The through holes may define abowl-like profile, for example.

An aluminum reflecting film 219 of a substantially uniform thickness isprovided to coat the upper surface of the upper ceramic substrate 203 aswell as the inner walls of the through holes 215 formed through theceramic substrate 203. With the provision of the aluminum reflectingfilm 219, reflectors (reflector holes) are formed. Each through hole 215is formed (designed) to have such a shape that white light emitted fromlateral sides of the semiconductor light emitting devices 10 isreflected by the aluminum reflecting film 219 in a directionsubstantially perpendicular to the main surface of the ceramic substrate203.

A pair of cathode pad 218 and an anode pad 220 (shown in FIG. 28B) isprovided at each location, on the upper surface of the ceramic substrate201, where a respective one of the semiconductor light emitting devices10 is to be mounted. Each pad is made up of copper (Cu) plated withnickel (Ni) and then with gold (Au). Each semiconductor light emittingdevice 10 is mounted with the base substrate 12 faced downward. Formounting, the second power supply terminal 44 is soldered to the cathodepad 218, whereas the first power supply terminal 42 is soldered to theanode pad 202. Instead of solder, gold bumps or a silver paste may beused for joining the power supply terminals to the pads.

The lenses 204, 206 and 208 are adhered to the ceramic substrate 203 byan adhesive agent 221. The adhesive agent 221 may be a silicone resin,an epoxy resin, or the like.

The three semiconductor light emitting devices 10 are connected inparallel by a wiring pattern formed on the upper surface of the ceramicsubstrate 201.

FIG. 28A is a plan view showing the LED module 200 without the lenses204, 206, and 208. In FIG. 28A, the three semiconductor light emittingdevices 10 are denoted with letters A, B, and C so as to distinguish onefrom another.

As described above, a pair of the anode pad 220 and the cathode pad 218(FIG. 28B) is provided at each location, on the upper surface of theceramic substrate 201, where a respective one of the semiconductor lightemitting devices 10A, 10B and 10C is to be mounted.

The anode pads 220 connected to the semiconductor light emitting devices10A, 10B and 10C are electrically connected to one another by a wiringpattern 236. The wiring pattern 236 is connected to the positiveterminal 212 at its end via a plated-through hole 237. Similarly, thecathode pads 218 connected to the semiconductor light emitting devices10A, 10B and 10C are electrically connected to one another by a wiringpattern 238. The wiring pattern 238 is connected to the negativeterminal 214 at its end via a plated-through hole 239. In other words,the semiconductor light emitting devices 10A, 10B and 10C are connectedin parallel via the wiring patterns 236 and 238.

The LED module 200 having the above structure is attached to theillumination fixture 240 to be ready for use. The LED module 200 and theillumination fixture 240 together constitute an illumination apparatus242.

FIG. 29A is a schematic oblique view and FIG. 29B is a bottom view ofthe illumination apparatus 242.

The illumination fixture 240 is fixed in a ceiling of a room, forexample. The illumination fixture 240 is provided with a power circuit(not illustrated) for converting an alternating current from acommercial power source (for example, 100 V, 50/60 Hz) to a directcurrent required to drive the LED module 200.

With reference to FIG. 30, a description is given to the structure forattaching the LED module 200 to the illumination fixture 240.

The illumination fixture 240 has a circular recess 244 for fitting theLED module 200 therein. The circular recess 244 has a flat bottom and aninner wall that is internally threaded (not illustrated) at a portionadjacent its opening. The illumination fixture 240 also has power supplyterminals 246 and 248 and a guide pawl 230 all of which have flexibilityand inwardly project from points on the inner wall between the threadedportion and the bottom. The power supply terminal 246 is a positiveterminal, whereas the power supply terminal 248 is a negative terminal.In addition, an upright guide pin 252 is provided at the center of thebottom of the circular recess 244.

For attachment of the LED module 200 to the illumination fixture 240,there are provided an O-ring 254 made of silicon rubber and a ring screw256. The ring screw 256 is substantially rectangular in cross sectionand has an externally threaded outer surface (not illustrated). Inaddition, the ring screw 256 has a notch 258 formed in thecircumferential direction.

Now, a description is given to an attachment procedure.

First, the LED module 200 is fit into the circular recess 244. At thetime of fitting, the LED module 200 is so positioned that (i) theceramic substrate 202 comes between the bottom surface of the circularrecess 244 and the power supply terminals 246 and 248, (ii) the guidepin 252 comes to enter the guide hole 216, and (iii) the guide notch 210engages with the guide pawl 230. Through the insertion of the guide pin252 into the guide hole 216, the LED module 200 is axially aligned withthe center of the circular recess 244. In addition, through theengagement between the guide notch 210 and the guide pawl 230, the powersupply terminals 246 and 248 are properly positioned relative to thepositive terminal 212 and the negative terminal 214.

After the LED module 200 is fit into the circular recess 244, the O-ring254 is placed and the ring screw 256 is screwed into the circular recess244 to secure the ring screw 256 in place. As a result, the positiveterminal 212 and the negative terminal 214 come into intimate contactwith the power supply terminals 246 and 248, respectively, therebyreliably establishing electrical connection. In addition, thesubstantially entire surface of ceramic substrate 202 is brought intointimate contact with the flat bottom surface of the circular recess244. Thus, heat generated by the LED module 200 is effectively conductedto the illumination fixture 240, thereby improving cooling effect of theLED module 200. To further improve the heat conductivity between the LEDmodule 200 and the illumination fixture 240, silicone grease may beapplied to the ceramic substrate 202 and the bottom surface of thecircular recess 244.

On application of an electric current from a commercial power source tothe illumination apparatus 242 having the above structure, each of theLED chips 14A-14C included in each semiconductor light emitting devices10 emit blue light. Part of the blue light is converted into yellowlight by the phosphor particles contained in the phosphor 16. The bluelight and yellow light is mixed to produce white light. The resultingwhite light is emitted through a respective one of the lenses 204, 206,and 208.

The semiconductor light emitting devices 10 included in the LED module200 (FIG. 26) may be structured without the base substrate 12 (FIG. 1).That is, the semiconductor light emitting devices 10 may be mounteddirectly onto the ceramic substrate 202 (FIG. 26). Naturally, whenmaking such a modification, it is necessary to appropriately modify theshapes of components, such as bonding pads and power supply terminals,to be disposed on the ceramic substrate 202. Here, the ceramic substrate202 serves as the base substrate of each semiconductor light emittingdevice 10. In the case where the LED module 200 includes LED chips 400or 500 each of which is not provided with a base substrate, it isapplicable to directly mount the LED chips 400 or 500 onto the ceramicsubstrate 202 and then form a phosphor layer to cover the LED chips.

Up to this point, the present invention has been described by way of theabove embodiments. It should be naturally appreciated, however, thepresent invention is not limited to the above specific embodiments andvarious modifications, including the following may be made.

In principle, each semiconductor light emitting device according to theabove embodiments has a light emitting element composed of asemiconductor multilayer structure, a first electrode, and a secondelectrode. The semiconductor multiplayer structure has the followinglayers in the stated order to constitute a diode: a first conductivelayer of a first conductive type and made of a p-semiconductor; a lightemission layer; a second conductive layer of a second conductive typeand made of an n-semiconductor. The second conductive layer is disposedon a light extracting side of the light emission layer. The first andsecond electrodes are in contact with the first and second conductivelayers, respectively. The semiconductor multilayer structureadditionally has a base substrate supporting the light emitting elementand a phosphor. The phosphor is disposed on the base substrate so as tocover the light emitting element and contains a phosphor material(phosphor particles) having a property of emitting light by absorbinglight emitted by the light emission layer. The base substrate has afirst power supply terminal and a second power supply terminal that areelectrically connected to the first and second electrodes, respectively.

(1) The first conductive layer may be a p-GaN layer or a p-AlGaN layeras described above. The second conductive layer may be an n-GaN layer oran n-AlGaN layer as described above. In the case where the firstconductive layer is made of a p-semiconductor, the second conductivelayer needs to be made of an n-semiconductor. Reversely, in the casewhere the first conductive layer is made of an n-semiconductor, thesecond conductive layer needs to be made of a p-semiconductor.

(2) As in the above embodiment 1, an InGaN/GaN MQW light emission layermay be used as the light emission layer for emitting light ranging fromblue (430-470 nm) to violet (380-430 nm). For emitting near-ultravioletlight (380 nm or shorter), an AlGaN/InGaN MQW light emission layer maybe used as in the embodiment 2.

(3) The first conductive layer, the light emission layer, and the secondconductive layer may be 0.1-0.5 μm thick, 0.01-0.1 μm thick, and 0.5-3μm thick, respectively. In addition, each of the first conductive layer,the light emission layer, and the second conductive layer may be made ofa single layer or multiple layers. In addition, such multiple layers maybe made of mutually different compositions.

(4) As described above, the single crystal substrate is disposed incontact with a main surface of either the first or second conductivelayer and used for epitaxially growing the semiconductor multilayerstructure. The single crystal substrate may be any of GaN, SiC, andsapphire substrates, and the thickness may be about 0.01-0.5 mm.

(5) The materials of the first and second electrodes are not limited.Yet, it is preferable to use a metal material containing, for example,Ni or Ti, which has a relatively low contact resistance with the firstor second conductive layer. For improving the light extractionefficiency of the semiconductor light emitting device, it is preferablethat the first electrode in contact with the first conductive layer bemade of a material reflecting light emitted from the light emissionlayer. For example, a stack of Rh/Pt/Au films used in the aboveembodiments is preferable. In the case where the second electrode isdisposed on a main surface of the second conducive layer serving as alight extracting surface, it is preferable that the second electrode bemade of a transparent conductive material, such as ITO, for improvinglight extraction efficiency. Each of the first and second electrodes maybe 0.01-3 μm thick.

(6) The material of the base substrate is not specifically limited. Forexample, the base substrate may be mainly made of a semiconductor suchas Si or SiC, a ceramic such as Al₂O₃ or AlN, or a metal such as Au, Al,or Cu. In the case where the base substrate is made of a semiconductoror a metal and thus needs to be insulated, it is applicable to disposean additional layer on the base substrate for insulation. Such anadditional layer may be made of: an oxide or nitride, such as a siliconoxide or a silicon nitride; a resin, such as epoxy; a composite materialcontaining a resin, such epoxy, and particles of a metal oxide, such asalumina; or a glass material.

In the case where the base substrate is made of a semiconductor materialsuch as Si, an electronic circuit may be integrally formed with the basesubstrate. The electronic circuit is for controlling a supply voltageand current to the semiconductor multilayer structure. In addition, itis applicable, regardless of the substrate material, to provideelectronic components on or within the base substrate. The basesubstrate may be about 0.1-1 mm thick. Preferably, the base substrate ismainly made of a material of which thermal conductivity is 1 W/K·m orhigher, more preferably 10 W/K·m or higher, or even more preferably 100W/K·m or higher. In addition, the shape of main surfaces of the basesubstrate is not limited to a rectangle, which is commonly used.Instead, the main surfaces may be in a polygonal shape, such as ahexagon used in the embodiment 1, or in a circular shape.

In the case where the base substrate of the embodiment 1 or 2 is made ofan HCP crystal substrate, the HCP crystal substrate can be divided intobase substrates each having a substantially hexagonal shape, withoutwasting the HCP crystal substrate except along the periphery where nomore regular hexagonal areas can be formed. That is, similarly toembodiments 3 and 4, the better use of the HCP crystal substrate isensured in manufacturing the base substrates of embodiments 1 and 2.

(7) The phosphor is made of a resin, such as silicone or epoxy, or aglass in which powder of phosphor materials is dispersed. The phosphorpowder emits light by absorbing light emitted from the light emissionlayer. Examples of phosphor materials emitting red light include(Ca,Sr)S:Eu²⁺, Sr₂Si₅N₈:Eu²⁺, BaSi₇N₁₀:Eu²⁺, CaAlSiN₃:Eu²⁺, La₂O₂S:Eu³⁺,and Y₂O₂S:Eu³⁺. Examples of phosphor materials emitting yellow lightinclude (Sr,Ba)₂SiO₄:Eu²⁺, (Y,Gd)₃Al₅O₁₂:Ce³⁺. Examples of phosphormaterials emitting green light include (Ba,Sr)₂Si₄:Eu²⁺,Y₃(Al,Ga)₅O₁₂:Ce³⁺, SrAl₂O₄:Eu²⁺, BaMgAl₁₀O₁₇:Eu²⁺, or Mn²⁺. Examples ofphosphor materials emitting blue light include (Ba,Sr)MgAl₁₀O₁₇:Eu²⁺,Mn²⁺, (Sr,Ca)₁₀(PO₄)₆Cl₂:Eu²⁺.

In the case where the light emission layer emits blue light, thephosphor needs to at least contain, in addition to a phosphor materialemitting yellow light, a phosphor material emitting red light. As aresult, the blue light is mixed with the yellow light and the red light,so that the phosphor emits white light. In the case where the lightemission layer emits violet or near-ultraviolet light, the phosphorneeds to at least contain, in addition to phosphor materials emittingblue and yellow light, phosphor materials emitting red and green light.As a result, the blue, green, yellow, and red light is mixed, so thatthe phosphor emits white light.

(8) In the embodiments 1 and 2 above, the cleavage guide grooves areformed in the main surface of the single crystal substrate facing awayfrom the semiconductor multilayer structure. Yet, it is applicable, asshown in the embodiments 3 and 4, to form the guide grooves of theembodiments 1 and 2 in the main surface of the single crystal substratefacing toward the semiconductor multilayer structure.

The reverse may hold as well. In the embodiments 3 and 4, the cleavageguide grooves are formed in the main surface of the single crystalsubstrate facing toward the semiconductor multilayer structure. Yet, itis applicable, as shown in the embodiments 1 and 2, to form the guidegrooves of the embodiments 3 and 4 in the main surface of the singlecrystal substrate facing away from the semiconductor multilayerstructure.

It is also applicable to form the guide grooves in both main surfaces ofthe single crystal substrate.

Similar description applies to the holes (holes 162, see FIG. 17) formedfor cleavage in addition to the guide grooves, in the case where theholes are non-through holes. That is, the holes may be formed in eitheror both main surfaces of the single crystal substrate.

(9) In addition to GaN, SiC, and sapphire substrates, AlN, ZnO, BN, andMgO are known to be usable materials for a semiconductor multilayerstructure (epitaxial layer) as well as for a substrate used forepitaxial growth of the semiconductor multilayer structure. The presentinvention is applicable to any of these materials as long as thematerial has an HCP single crystal structure.

(10) In the above embodiments, the descriptions are given by way of blueLED and UV LED chips as examples of the semiconductor light emittingelements. Needless to say, however, the present invention is not limitedto any specific emission color. As long as the semiconductor multilayerstructure (epitaxial layer) and the single crystal substrate are of anHCP single crystal structure, the present invention is applicableirrespective of the emission color.

(11) In the embodiments 1 and 2, the LED chips are used in combinationwith a phosphor. Yet, also in the case of LED chips used withoutprovision of a phosphor, a semiconductor light emitting device producinga beam spot closer to a circle is manufactured, while ensuring the bestpossible use of the semiconductor material.

INDUSTRIAL APPLICABILITY

A semiconductor light emitting device according to the present inventionis suitably applicable to the fields of illumination in which a beamspot is desired to be as closer to a circle as possible. The fields ofillumination cover indoor illumination as well as outdoor illuminationincluding streetlights and vehicle headlights.

The invention claimed is:
 1. A semiconductor light emitting devicecomprising: a single crystal substrate with a hexagonal closest-packedcrystal structure having a (0001) plane on a main surface; and asemiconductor multilayer structure that includes a light emission layerand is formed on the main surface of the single crystal substrate; wherein plan view, the single crystal substrate has a hexagonal shape witheach vertex cut away to leave an arc-shaped recess that curves inwardtowards the center of the single crystal substrate, and each sidesurface of the single crystal substrate is a cleavage plane.
 2. Thesemiconductor light emitting device according to claim 1, wherein thesingle crystal substrate is made of one of GaN and SiC.
 3. Thesemiconductor light emitting device according to claim 2, furthercomprising: a first electrode formed on a second main surface of thesemiconductor multilayer structure facing away from the single crystalsubstrate; and a second electrode formed on a main surface of the singlecrystal substrate facing away from the semiconductor multilayerstructure.
 4. The semiconductor light emitting device according to claim3, Wherein in plan view, the semiconductor multilayer structure has ahexagonal shape that is slightly smaller than the single crystalsubstrate.
 5. The semiconductor light emitting device according to claim4, wherein the first electrode includes: a transparent electrode whichis a coating formed on the main surface of the semiconductor multilayerstructure; and a contact electrode formed on the transparent electrode,wherein the contact electrode is composed of a hexagonal rim portion andspoke portions radially extending from a center of the contact electrodeto vertexes of the hexagonal rim.
 6. The semiconductor light emittingdevice according to claim 1, wherein in plan view, the semiconductormultilayer structure has a hexagonal shape that is slightly smaller thanthe single crystal substrate.
 7. The semiconductor light emitting deviceaccording to claim 6, further comprising: a transparent electrode formedon a main surface of the semiconductor multilayer structure facing awayfrom the single crystal substrate; and a contact electrode formed on thetransparent electrode, wherein the contact electrode is comprised of ahexagonal rim portion and a spoke portion extending from a center of thecontact electrode to the vertexes of the hexagonal rim.
 8. Thesemiconductor light emitting device according to claim 1, furthercomprising: a first electrode formed on a second main surface of thesemiconductor multilayer structure facing away from the single crystalsubstrate; and a second electrode formed on a main surface of the singlecrystal substrate facing away from the semiconductor multilayerstructure.
 9. The semiconductor light emitting device according to claim1, further comprising: a transparent electrode formed on a main surfaceof the semiconductor multilayer structure facing away from the singlecrystal substrate; and a contact electrode formed on the transparentelectrode, wherein the contact electrode is composed of a hexagonal rimportion and a spoke portion extending from a center of the contactelectrode to the vertexes of the hexagonal rim.
 10. A semiconductorlight emitting device comprising: a single crystal substrate with ahexagonal closest-packed crystal structure having a (0001) plane on amain surface; and a semiconductor multilayer structure that includes alight emission layer and is formed on the main surface of the singlecrystal substrate; where in plan view, the single crystal substrate hasa hexagonal shape with each vertex cut away to leave an arc-shapedrecess that curves inward towards the center of the single crystalsubstrate, the arc-shaped recesses are only provided on the singlecrystal substrate, and each side surface of the single crystal substrateis a cleavage plane.
 11. The semiconductor light emitting deviceaccording to claim 10, wherein the single crystal substrate is made ofone of GaN and SiC.
 12. The semiconductor light emitting deviceaccording to claim 11, further comprising: a first electrode formed on asecond main surface of the semiconductor multilayer structure facingaway from the single crystal substrate; and a second electrode formed ona main surface of the single crystal substrate facing away from thesemiconductor multilayer structure.
 13. The semiconductor light emittingdevice according to claim 12, wherein in plan view, the semiconductormultilayer structure has a hexagonal shape that is slightly smaller thanthe single crystal substrate.
 14. The semiconductor light emittingdevice according to claim 13, wherein the first electrode includes: atransparent electrode which is a coating formed on the main surface ofthe semiconductor multilayer structure; and a contact electrode formedon the transparent electrode, wherein the contact electrode is composedof a hexagonal rim portion and spoke portions radially extending from acenter of the contact electrode to vertexes of the hexagonal rim. 15.The semiconductor light emitting device according to claim 10, whereinin plan view, the semiconductor multilayer structure has a multi layerhexagonal shape that is slightly smaller than the single crystalsubstrate with each vertex of the multilayer hexagonal shape alignedwith an arc-shaped recess of the single crystal substrate.
 16. Thesemiconductor light emitting device according to claim 15, furthercomprising: a transparent electrode formed on a main surface of thesemiconductor multilayer structure facing away from the single crystalsubstrate; and a contact electrode formed on the transparent electrode,wherein the contact electrode is comprised of a hexagonal rim portionand a spoke portion extending from a center of the contact electrode tothe vertexes of the hexagonal rim of the multilayer hexagonal shape. 17.The semiconductor light emitting device according to claim 10, furthercomprising: a first electrode formed on a second main surface of thesemiconductor multilayer structure facing away from the single crystalsubstrate; and a second electrode formed on a main surface of the singlecrystal substrate facing away from the semiconductor multilayerstructure.
 18. The semiconductor light emitting device according toclaim 10, further comprising: a transparent electrode formed on a mainsurface of the semiconductor multilayer structure facing away from thesingle crystal substrate; and a contact electrode formed on thetransparent electrode, wherein the contact electrode is composed of ahexagonal rim portion and a spoke portion extending from a center of thecontact electrode to the vertexes of the hexagonal rim.